cp's OEIS Frontend

A215784 Number of permutations of 0..floor((n*6-1)/2) on even squares of an n X 6 array such that each row, column, diagonal and (downwards) antidiagonal of even squares is increasing.

%I A215784 #8 Jul 23 2018 06:16:55
%S A215784 1,2,12,29,189,458,2988,7241,47241,114482,746892,1809989,11808549,
%T A215784 28616378,186696108,452432081,2951712081,7153064162,46667304972,
%U A215784 113091730349,737821743309,1788008493098,11665145978028,28268860698521
%N A215784 Number of permutations of 0..floor((n*6-1)/2) on even squares of an n X 6 array such that each row, column, diagonal and (downwards) antidiagonal of even squares is increasing.
%C A215784 Column 6 of A215788.
%H A215784 R. H. Hardin, <a href="/A215784/b215784.txt">Table of n, a(n) for n = 1..210</a>
%F A215784 Empirical: a(n) = 16*a(n-2) - 3*a(n-4).
%F A215784 Empirical g.f.: x*(1 + 3*x)*(1 - x - x^2) / (1 - 16*x^2 + 3*x^4). - _Colin Barker_, Jul 23 2018
%e A215784 Some solutions for n=4:
%e A215784 ..0..x..1..x..3..x....0..x..1..x..3..x....0..x..1..x..2..x....0..x..1..x..2..x
%e A215784 ..x..2..x..5..x..8....x..2..x..5..x..7....x..3..x..4..x..6....x..3..x..4..x..5
%e A215784 ..4..x..6..x..9..x....4..x..6..x..9..x....5..x..7..x..9..x....6..x..7..x..9..x
%e A215784 ..x..7..x.10..x.11....x..8..x.10..x.11....x..8..x.10..x.11....x..8..x.10..x.11
%Y A215784 Cf. A215788.
%K A215784 nonn
%O A215784 1,2
%A A215784 _R. H. Hardin_, Aug 23 2012